A planet believed to be remarkably similar to Earth has been discovered orbiting a distant sun-like star，bolstering hopes of finding life elsewhere in the universe, US scientists said on Thursday. The planet, which is about 60 percent larger than Earth, is located 1400 light years away in the constellation Cygnus. It was discovered by astronomer using NASA's kepler space telescope and it circles a star that is similar to size and temperature to the sun, but older.
“In my mind, this is the closest thing we have to another planet like the Earth," astronomer Jenkins told reporters on a conference call, "It's simply awe-inspiring to consider that this planet, Kepler-452b, has spent 6 billion years in the habitable zone of its star. That's considerable time and opportunity for life exist on this planet." he said. Kepler- 452b is positioned as far from its parent star as Earth is from the sun, completing an orbit in 385 days, compared to Earth's 365-day orbit.At that distancc,surface temperature would be suitable for liquid water, a condition to be believed critical for life.
Scientists previously have found Earth-sized planets orbiting in stars'so-called"habitable zones", but those stars are cooler and smaller than the sun, a G2 type yellow star. NASA launched the Kepler telescope in 2009 to survey a sampling of nearby stars in an attempt to learm if planets like Earth were common in the galaxy.
“This is great great progress in finding a planet like Earth that is similar in size and temperature around non-like star,"”said Kepler scientist Jeff Coughlin, "With a rations 60 percent larger than the Earth, this planet has a somewhat better chance of being rocky."Jeff said, though this conclusion is based on statistic analysis and computer modeling, not direct evidence. If so,Kepler-452b could be about five times as massive as Earth and has gravity that is twice as strong as what exists on Earth surface. The planet also could have a thick atmosphere, cloudy skies an dactive volcanoes, Jenkin said.
With the discovery of Kepler-452b, the telescope has found 1030 confirmed planets include 11 other near-Earth twins,none of which circle sun-like stars. The telescope cannot see planets directly, but measures minute in light coming from target stars. Sophisticated computer programs and follow- up observations with ground based telescopes then determine if some of the light dips are caused by planets passing in front of their parent stars, relative to Kepler's linc of sight.
Attempts to learn if Kepler-452b has an atmosphere likely will have to wait for a new generation of more sensitive space telescope, said NASA's associate administrator John Grunsfeld.
It can be inferred from the passage that——

A.of all the stars discovered so far, Kepler-452b is the most similar to the Earth
B.previously found the Earth-sized planets orbiting in stars'"habitable zones' are suitable forlife
C.if Kepler-452b is rocky, it could have gravity twice as strong as what exists on Earth' 'ssurface
D.now people have found 12 Earth-like planets circling sun-like stars

答案： A

本题解析：暂无解析

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